a. Field of the Invention
The present invention relates to an adsorber for humidity and odorous gas exchange such as an adsorbing sheet for dehumidification and to a honeycomb adsorbing element for humidity and odorous gas exchange such as an adsorbing element for dehumidification or an adsorbing element for humidity and sensible heat exchange (called a humidity exchanging body hereinafter).
b. Description of the Prior Art
A honeycomb element using inorganic humidity adsorbing agents such as molecular sieves like zeolite, silica gel and lithium chloride for dehumidification or total heat (humidity and sensible heat) energy exchange, has been used. And the present applicants manufacture and sell humidity and odorous gas exchangers in which silica gel or metal silicate gel is synthesized by chemical reaction of acid or aqueous solution of metallic salt after impregnating a laminate with water glass which is then rigidly adhered (Japanese Pat. No. 1,542,374 and the U.S. Pat. No. 4,911,775). These adsorbers for dehumidification are used for removing humidity from gases such as air and nitrogen gas in various fields such as semiconductor industry, film industry, food industry and army. A honeycomb element for total heat energy exchange is used as a total heat energy exchanger for buildings, factories and houses for exchanging humidity and sensible heat simultaneously.
The prior adsorbents such as molecular sieves like zeolite and silica gel mentioned above are dispersed in binders such as silica sol and alumina sol. A honeycomb element is soaked in this dispersion to impregnate minute particles of the inorganic humidity adsorbing agents mentioned above in the sheet that forms the honeycomb element and to fix them rigidly in the sheet. Or in another prior method, minute particles of inorganic humidity adsorbing agents are fixed rigidly by using binders to the sheet that forms the honeycomb element, which sheet is then laminated and shaped in honeycomb structure. In such methods, binders decrease adsorbing area of adsorbents, lowering their adsorbing ability rather than contribute to humidity adsorption. The present invention is to obtain a high efficiency humidity adsorbing sheet and a honeycomb element for humidity and odorous gas exchange by a method as simple as to impregnate one kind of particular silica sol, thus solidify by gelatinize, without using minute particles of such inorganic humidity adsorbing agents nor binders for binding these agents.
The present invention is to obtain a humidity exchanging body by using silica sol which contains silica particles of diameter not larger than approximately 120 xc3x85, having numerous stable silanol radicals on the surface, or by adding various other adsorbents are added to the silica sol, impregnating or coating the mixture to a sheet or to a laminate with numerous small channels (called a honeycomb laminate hereinafter), and by drying it to gelatinize and to fix rigidly minute particles of silica in fiber gaps of and on the surface of the sheet in the laminate.
The silica sol used here contains as solid content not more than 30% of minute particles of silica of diameter not larger than approximately 120 xc3x85 having numerous silanol radicals on the surface. When this sol is gelatinized by drying by means of heating or others, minute particles of silica are bound in porous structure, binding to one another, to form micropores. These micropores, with numerous silanol radicals on the surface of minute particles of silica, exhibit strong moisture adsorbing ability. When the diameter of particles in silica sol is big, the diameter of micropores formed by linking of the particle becomes too big, so their moisture adsorbing effect is decreased and linking force of the particles is weakened. Therefore it is unsuitable to be used as a honeycomb humidity adsorbing body. On the other hand very small amount of alkali metal ion contained in silica sol also contributes to moisture adsorbing ability. Therefore used is sol into which a comparatively large amount of this, too, is mixed. Examples are explained below in detail.